Dan Kent Posted January 28, 2014 Report Share Posted January 28, 2014 Hey folks I need some help. I just picked up my plane from it's annual. Everything seems fine (I got the Dynon radio installed and so far really like it). Before flying home I did a test flight with the distributor of my airplane. Upon taxiing out to take off the plane started bouncing. I thought the plane had sat in cold weather for a while and the tires had developed a flat spot that would work its way out with more taxiing and that possibly the tires were low on air. The bouncing stopped on the takeoff roll. Test flight went fine, go the plane home and went flying this past Sunday. Before flying I checked the tire pressure on the mains and it was 29 psi. I fill them up to 35 psi (using the Dresser 6 ply tires). I had a fairly long taxi to take off and the bouncing was present again but not quite as severe, and thought over time it would smooth out. I took off and flew to a nearby field and did 3 full stop landings. Each time taxiing back to takeoff the bouncing would happen but only between 7-9 kts ground speed. Below this it was smooth and above this it was smooth. I contacted the mechanic that worked on the plane and he doesn't have any suggestions. He did change the brake pads on the left main, but it is not pulling when brakes are applied (I have toe brakes so I can brake each main differently). Also upon liftoff there is no vibration, which would indicate a wheel/tire balance problem. I was going to remove the tire pants this weekend and do a visual inspection and do some taxiing without them to see if the problem is still there. I was then going to put more air in them (probably 40 psi) to see if this diminishes the issue. Any ideas or suggestions? Link to comment Share on other sites More sharing options...
Doug G. Posted January 28, 2014 Report Share Posted January 28, 2014 I think you need to read that again Roger. Unless CTs came with toe brakes he is talking about a different setup. Link to comment Share on other sites More sharing options...
Dan Kent Posted January 28, 2014 Author Report Share Posted January 28, 2014 Sorry I forgot to mention, I have a TL Ultralight Sting S4 (low wing). The wheels are very similar to Beringer but not exactly their wheel. I think they are from the airplane manufacturer, TL Ultralight. The plane has 200 hours on it. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted January 28, 2014 Report Share Posted January 28, 2014 Sorry I forgot to mention, I have a TL Ultralight Sting S4 (low wing). The wheels are very similar to Beringer but not exactly their wheel. I think they are from the airplane manufacturer, TL Ultralight. The plane has 200 hours on it. Still sounds like a front suspension issue, I'd look at whatever cushions the nose wheel first. Link to comment Share on other sites More sharing options...
Dan Kent Posted January 28, 2014 Author Report Share Posted January 28, 2014 Will look at the nose wheel also, but it sure felt like the mains as I sit ahead of them and my recollection is that the movement was behnd me - if that makes sense. It also seemed more pronounced with another person in the plane, but I also had lower tire pressure when I had someone with me. Link to comment Share on other sites More sharing options...
Tom Baker Posted January 28, 2014 Report Share Posted January 28, 2014 It sounds like the tire is out of round from sitting. I have felt this in a CT before. It gets worse if both flat spots get line up in unison. Link to comment Share on other sites More sharing options...
Dan Kent Posted January 28, 2014 Author Report Share Posted January 28, 2014 Thanks Tom. That was my thought but after doing several takeoffs and landings I thought they would have gotten back to a normal shape but didn't and also it disappeared above 9 kts. Link to comment Share on other sites More sharing options...
Dan Kent Posted February 5, 2014 Author Report Share Posted February 5, 2014 Update: I went to the airport last weekend and took off the wheel pants and inspected both mains inside and out. Everything appears normal (no bulges, lumps, wear points, flat spots). I was unable to jack the plane up but did roll the plane forward several rotations and didn't notice any noise (bad bearing, or brakes rubbing). I intending to fly this weekend so we'll see if it is still there. If so, then I'll make a jig and jack the plane up. Link to comment Share on other sites More sharing options...
Tom Baker Posted February 5, 2014 Report Share Posted February 5, 2014 If you don't have a way to jack the airplane I would make or get something now instead of waiting until you need it. Link to comment Share on other sites More sharing options...
Roger Lee Posted February 5, 2014 Report Share Posted February 5, 2014 You don't need any special jack. Just use a 6' "A"frame ladder with a towel or blanket on it to prevent scratches and place it under the wing next to the tie down ring is. We have been doing that for 8 years and works fine. I also have an engine lift with a tire mounted on top. You can use that to lift a wing too. Link to comment Share on other sites More sharing options...
Tom Baker Posted February 5, 2014 Report Share Posted February 5, 2014 You don't need any special jack. Just use a 6' "A"frame ladder with a towel or blanket on it to prevent scratches and place it under the wing next to the tie down ring is. We have been doing that for 8 years and works fine. I also have an engine lift with a tire mounted on top. You can use that to lift a wing too. Roger, not everbody has a CT. I think a 6' ladder might be a bit tall for his Sting. Link to comment Share on other sites More sharing options...
Roger Lee Posted February 5, 2014 Report Share Posted February 5, 2014 Hi Tom, You have a good point. Forgot about that. I use an automotive floor jack with wood underneath for height and jack it up under the leg at the fuselage. It's a good solid jack point. Link to comment Share on other sites More sharing options...
Dan Kent Posted February 6, 2014 Author Report Share Posted February 6, 2014 The distributor's mechanic has someone lift the wing and slide a padded table under the wing, but I'm not able to do this. I still think Tom was right and that it was a flat spot from sitting too long in the cold, and hope it will not be there this weekend. A floor jack won't fit under the butt end of the gear leg, as the brake caliper is on the bottom and the space available to get a jack in is about 1", so it has to be some sort of device to lift the wing. Link to comment Share on other sites More sharing options...
FastEddieB Posted February 6, 2014 Report Share Posted February 6, 2014 Just an outside perspective... Most planes have designated "jacking points". On the Cirrus, you unscrewed the wing tiedown ring, and Cirrus provided a screw-in pad to safely lift the plane. On my Sky Arrow, the composite gear goes straight out a few inches before bending down, designated as a jacking point. Maybe not all planes have them, but lacking one on a CT seems an oversight - I mean, removing a wheel for maintenance or emergency repair is a fairly common occurence, so there should be an impromptu way to accomplish it. Link to comment Share on other sites More sharing options...
Anticept Posted February 6, 2014 Report Share Posted February 6, 2014 It states in the maintenance manual where you should jack it. It says close to the tie down ring on the spar using padding, such as with a ladder (very common). It also says if you have to jack the plane elsewhere, such as the belly, you have to use padding and spread it out as much as possible. Link to comment Share on other sites More sharing options...
FastEddieB Posted February 6, 2014 Report Share Posted February 6, 2014 For perspective: That's Jon Hansen, effecting my axle spacer replacement. Link to comment Share on other sites More sharing options...
Dan Kent Posted February 10, 2014 Author Report Share Posted February 10, 2014 Another update: Went out flying yesterday (after waiting 3 hours for the ceiling to get high enough) and the problem seems to be disappearing slowly. While taxiing yesterday it was still between 6 and 9 kts, but hardly noticeable. In fact if I hadn't been aware of the issue I might not have noticed it. I now think it is a flat spot on the tires that is slowly working it way out. It was less pronounced after 4 touch and go's then when I first taxied out. Link to comment Share on other sites More sharing options...
Dan Kent Posted February 11, 2014 Author Report Share Posted February 11, 2014 You could also check the wheel bearings. If worn or wiped out they can also cause the wheel to roll out of round. I was considering this, but decided to wait and see if it self corrects because I just had my annual and the mechanic, who I trust, removed both wheels and inspected the brakes (he replaced a set of brake pads, but only on one side). Link to comment Share on other sites More sharing options...
Roger Lee Posted February 11, 2014 Report Share Posted February 11, 2014 Dan, Who's brakes do you have on your plane? If they are standard round bearings no big deal, if they are tapered roller bearings like Matco he may have the axle nut that applies pressure to the bearings too loose. Common mistake. Link to comment Share on other sites More sharing options...
Dan Kent Posted February 12, 2014 Author Report Share Posted February 12, 2014 Roger, According to the maintenance manual the brakes are by TL Ultralight (the manufacturer of the plane). The master equipment list allows either these or Matco or Grove. My brake fluid resevoir was a little low and in researching the correct brake fluid I discovered that I do not have Matco brake cylinders (takes a different fluid than mine) so my guess is that they are not Matco. I also think they are standard round bearings as I observed the mechanic last year when he changed my tires and I don't recall them being tapered. Here's some pictures out of the maintenance manual or the brakes. Link to comment Share on other sites More sharing options...
Roger Lee Posted February 13, 2014 Report Share Posted February 13, 2014 Hi Dan, Interesting. I have not seen a set of brakes like this. Link to comment Share on other sites More sharing options...
Dan Kent Posted February 13, 2014 Author Report Share Posted February 13, 2014 I think the design is very similar to Beringer's. catPlaneUS 2013.pdf Link to comment Share on other sites More sharing options...
FastEddieB Posted February 13, 2014 Report Share Posted February 13, 2014 I thought the same thing. As seen on a new Sky Arrow at Oshkosh: Link to comment Share on other sites More sharing options...
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